Overview

Conduct disorder (CD) is one of the most difficult and intractable mental health problems in children and adolescents. CD involves a number of problematic behaviors, including oppositional and defiant behaviors and antisocial activities (eg, lying, stealing, running away, physical violence, sexually coercive behaviors).

A preventable predisposing factor for the development of all mental health disorders in children and adolescents has been found in a cross-sectional survey involving second-hand smoke exposure in youth who are not themselves cigarette smokers. The study adjusted for poverty, race/ethnicity, sex, asthma, hay fever, and maternal smoking; serum cotinine level was positively associated with CD, especially for non-Hispanic white males.
[1]

Males with conduct disorder and aggression have brain-based differences that resemble the differences found in persons with addiction, as compared with normally developing controls, regarding brain structure and function.
[2]

Studies have shown that females with conduct disorder as compared with subjects without conduct disorder have similar abnormal (disrupted) brain function to that previously observed in males, who tend to have increased aggression and conduct disorder; however, more research is needed to tease out factors such as child abuse that might cause similar findings.
[3]

These differences may be due to genetic differences in DNA methylation,
[4] which result in deficits in the perception of emotions and impairment in affect regulation, and this may cause early impairment in attachment that might possibly further interfere with the normative development of empathy, despite intellectual capacity for those cognitive functions.
[5]

Areas deep in the brain, especially the amygdala and insula, appear to exhibit abnormal function reflected in overall decreases in resting state connectivity and smaller overall size.
[7] This decrease in brain structure and functionality is also seen in youth with other diagnoses such as in cases of child abuse and neglect, causing reactive attachment disorder and temper dysregulation as well as schizophrenia, which makes careful attention to the differential of rule-breaking behaviors important for accurate diagnosis.
[8]

Recent research has found a possible association of changes in the dorsal mode default network connectivity with callous unemotional traits in conduct disorder.
[9]

This disorder is marked by chronic conflict with parents, teachers, and peers and can result in damage to property and physical injury to the patient and others. These patterns of behavior are consistent over time.

Behaviors used to classify CD fall into the 4 main categories of (1) aggression toward people and animals; (2) destruction of property without aggression toward people or animals; (3) deceitfulness, lying, and theft; and (4) serious violations of rules.

CD usually appears in early or middle childhood as oppositional defiant behavior. Nearly one half of children with early oppositional defiant behavior have an affective disorder, CD, or both by adolescence. Thus, careful diagnosis to exclude irritability due to another unrecognized internalizing disorder is important in childhood cases. Evaluation of parent-child interactions and teacher-child interactions is also critical. Even in a stable home environment, a small number of preschool-aged children display significant irritability and aggression that results in disruption severe enough to be classified as CD.

Diagnostic Criteria (DSM5)

In conduct disorder, a repetitive and persistent pattern of behavior occurs in which the basic rights of others or major age-appropriate societal norms or rules are violated. This manifests as the presence of at least 3 of the following 15 criteria in the past 12 months from any of the categories below, with at least one criterion present in the past 6 months:
[10]

Aggression to people and animals:

Often bullies, threatens, or intimidates others

Often initiates physical fights

Has used a weapon that can cause serious physical harm to others (eg, a bat, brick, broken bottle, knife, gun)

If the individual is age 18 years or older, criteria are not met for antisocial personality disorder.

Specify the following:

312.81(F91.1) Childhood-onset type: At least one symptom prior to age 10 years

312.82 (F91.2) Adolescent-onset type: No symptoms prior to age 10 years

312.89 (F91.9) Unspecified onset: Not enough information to determine whether the onset of the first symptom was before or after age 10 years

With limited prosocial emotions: An individual must have displayed at least 2 of the following characteristics persistently over at least 12 months and in multiple relationships and setting. These characteristics reflect the individual’s typical pattern of interpersonal and emotional functioning over this period and not just occasional occurrences in some situations. Thus, to assess the criteria for the specifier, multiple information sources are necessary. In addition to the individual’s self-report, it is necessary to consider reports by others who have known the individual for extended periods of time (eg, parents, teachers, coworkers, extended family members, peers).

Added specifier: Specify whether there is the presence of a lack of remorse or guilt. The person does not feel bad or guilty when he or she does something wrong (exclude remorse when expressed only when caught and/or facing punishment). The individual shows a general lack of concern about the negative consequences of his or her actions. For example, the individual is not remorseful after hurting someone or does not care about the consequences of breaking rules.

Oppositional defiant disorder (ODD) is discriminated from CD based on the defiance of rules and argumentative verbal interactions involved in ODD; CD involves more deliberate aggression, destruction, deceit, and serious rule violations, such as staying out all night or chronic school truancy.

The childhood-onset type is defined by the presence of 1 criterion characteristic of CD before an individual is aged 10 years; these individuals are typically boys displaying high levels of aggressive behavior. These individuals often also meet criteria for attention deficit/hyperactivity disorder (ADHD). Poor peer and family relationships are present, and these problems tend to persist through adolescence into adult years. These children are more likely to develop adult antisocial personality disorder than individuals with the adolescent-onset type.

Adolescent-onset type is defined by the absence of any criterion characteristic of CD before an individual is aged 10 years. These individuals tend to be less aggressive and have more normative peer relationships. They often display their conduct behaviors in the company of a peer group engaged in these behaviors, such as a gang. These patients are less likely to fit criteria for ADHD; however, the diagnosis of ADHD is still possible. These individuals are also far less likely to develop adult antisocial personality disorder. While boys are identified more often, the estimated sex ratio of this type of CD approaches 50% for girls and boys in some communities. The prognosis for an individual with adolescent-onset type is much better than for a person with the childhood-onset type.

CD is highly resistant to treatment. It follows a clear developmental path with indicators that can be present as early as the preschool period. Treatment is more successful when initiated early and must include medical, mental health, and educational components as well as family support. Close communication between home and school is particularly important at younger ages.
[11]

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Frequency

In the United States, prevalence rates for conduct disorder (CD) are estimated at 2–9%—5 out of every 100 teenagers—according to various nonclinical samples summarized by Costello in 1990, and are complicated by relatively high rates of co-occurrence or comorbidity with other disorders.
[12] A high degree of overlap among all of the externalizing disorders (ie, CD, ODD, ADHD) exists. Some researchers have indicated that the less severe disorders, such as ODD, simply may be the developmental precursor or a milder form of CD. However, CD is qualitatively different because it clearly involves aggression or other behaviors in which the basic rights of others or common social norms are violated repeatedly.

CD has no lower age limit. In a child younger than 10 years, the repetitive presence of only 1 of the 15 behaviors in the DSM5 is sufficient for the diagnosis. Thus, even a preschooler who demonstrated repetitive serious aggression, with intent to harm, meets the criteria for CD. The professional must be careful not to overuse this serious label, especially when considering young children with problematic behavior with discernible cause and with reasonable treatment potential.

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Clinical Course

The outcome cluster of problematic behaviors that produce the syndrome of conduct disorder (CD) is the result of both difficult temperamental characteristics of children and environmental influences that shape the existing temperament.

Very early disturbances

As early as when an individual is aged 2 years, signs (eg, irritable temperament, poor compliance, inattentiveness, impulsivity) can lead to patterns of behavior that result in disturbances of conduct at later ages. These very early disturbances can lead initially to the diagnosis of ADHD or ODD and later, or for more severe cases, to the diagnosis of CD. For some children who have severe temperamental difficulties (eg, irritability, high activity, poor attachment), oppositional behavior and conduct problems occur despite good efforts by parents to work with the child. However, more often these children have been part of unstable families that move often and experience economic stress.

Sometimes, a history of parent psychopathology, including conduct and legal problems, is present. For many individuals with CD, parenting is punitive and ineffective, often triggered by an irritable temperament in the child. However, recognizing that depressed and anxious parents are also punitive, inconsistent, and impatient even with the typical demands of parenting is important. Further, young children respond to depressive inaction by acting up in an effort to energize their parents. According to the model of coercive family processes, stressful conditions (eg, financial problems, marital problems, poor parenting skills, child irritability) make it difficult for parents to set limits effectively and consistently or to support their children emotionally.

Often, because of the child's temperamental difficulties (eg, hyperactivity, rigid and irritable behavior patterns), even parents with the best of intentions become involved in a negative cycle. In this cycle, children resist complying with requests, and parents either give in to the child or resort to more intensive punishment to gain compliance. When the parents relinquish control, the child's defiant and hostile behavior is strengthened; when the parents resort to more severe punishment, that type of control is reinforced in the parent but is used inconsistently. Severe physical punishment also is modeled for the child, who then reacts with physical aggressiveness as an immediate coping mechanism.

As a consequence of this pattern, parents often increasingly isolate themselves from outside support in the family and community. Parents become reluctant to take their child with CD out in public because they fear an uncontrollable incident with the child. After increased negative interaction with the child, parental stimulation may decrease as the parent spends less time with the child. In these situations, children with CD do not have sufficient opportunities to learn to accurately identify their strong emotions or to develop necessary self-control skills.

Elementary school progression

As the children advance to elementary school age, those with conduct problems tend to have continued aggressive tendencies with other adults and peers; these children lack the social skills to interact with peers. Children with CD tend to be aggressive, do not pay attention to social cues, often misinterpret other children as being hostile, and lack the ability to solve difficult social issues.

By the time they reach late latency age to early adolescence, in conflict situations, these children tend to have episodes of intense anger and resort to aggressive actions rather than verbally mediated responses. In these situations, they almost always blame peers for their own actions (eg, "He made me hit him.") and seldom take responsibility for their own actions.

Middle and high school progression

By middle school age, the 3 classes of behavior identified by Patterson and Forgatch's extensive clinical research are (1) noncompliance with commands, (2) emotional overreaction, and (3) failure to take responsibility for one's own actions. This cluster is at the core of conduct problems. In interviewing a child and family, reviewing these 3 specific areas is often helpful.
[13]

Along with the interpersonal problems at home and in school, academic and achievement problems that start as early as kindergarten are often present. Children who develop CD may receive less cognitive stimulation from their parents as a result. The parents spend less time with them because of the difficult interactions, which may contribute to low levels of academic readiness at school entry.

As the child advances in school, additional noncompliance with adults creates child-teacher interaction problems that also may result in less cognitive stimulation. In addition, comorbidity with ADHD may impede learning. The combination of these issues results in poor academic performance, often in a child who is perceived by others as having at least average intellectual skills. Untreated and without intervention, these children often are failing by the time they reach middle school.

If difficulties in the preschool period have been present, frequently the families provide poor support of academic performance. In communities with a number of distressed families, high-risk children may attend schools with a large number of other high-risk children, which creates a difficult learning climate and elicits further conduct problems.

As children with CD move into middle school, problems can intensify. Their continued aggression makes them unattractive to peers, who reject them at a time in their lives when peer relationships are becoming critically important. If these children continue to exhibit aggressive and noncompliant behavior in the classroom, teachers and other school staff also may reject them. Increasingly, parents of a child with CD may have negative interactions with school staff because of the child's behavior, which leads parents to further reject the child and have little interest in the child's activities, friends, and accomplishments as adolescence is reached.

Paradoxically, this rejection by school and parents often leads to more unstructured and unsupervised time and further opportunities for trouble. If students perform poorly in school, they no longer attempt to excel academically, and they develop negative self-thoughts about their own abilities and makes them more likely to associate with "bad friends" (ie, peers who are negative influences and also have similar deficits in empathy, emotion regulation, and prefer to engage in alcohol or other substance use instead of engaging in prosocial behaviors such as spiritual clubs and community service projects). The more risky behaviors these youth engage in, the more likely it is for them to become more and more risk-taking. Studies of neural processing show that risk-taking may be associated with reward-related brain activation, with risk-taking behaviors and the opposite of what normally should happen (ie, hypoactivation with disappointment losses).
[14]

In middle and early high school, depression is often identified in this group; this depression is secondary to years of social and academic failure. In middle school, children with CD are likely to join deviant peer groups (eg, gangs) and reject other types of positive social groups (eg, those associated with churches, sports, scouting, the arts). By adolescence, if untreated, the child with CD has been alienated from a family culture, successful school orientation, and other types of positively oriented groups and is likely to be associated with deviant peers.

Considerable research indicates that the deviant peer group provides training in criminal and delinquent behavior including substance abuse. At this point, parents who have been unable to supervise and control these children through the preschool and elementary school years are even less likely to be able to control and monitor their child's activity.
[15]

Children with CD are poorly bonded to family, school, or even to broader social rules. At this stage, they often come to the attention of the juvenile justice system. Unfortunately, if arrested and incarcerated, experiences in those self-contained facilities with other deviant peers often worsen the behaviors. A body of research indicates that group therapy programs for adolescents with conduct problems may worsen the problems by providing mutual reinforcement with the discussion of criminal behavior. Girls as well as boys are at risk for delinquent behaviors once they begin exhibiting conduct disorder symptoms, although boys tend to out represent girls, and sports participation may, to some degree, mediate this trajectory.
[16, 17]

Some residential programs administered by the juvenile justice system send these adolescents to military style camps (ie, boot camps) for periods from 4 weeks to 6 months. These boot camp programs are quite popular, and often the adolescents do well at home immediately after discharge or release. Unfortunately, the long-term data from such programs indicate poorer outcomes in the young adult years, with lower rates of employment and significantly higher rates of felony arrests.

A subgroup of youth with conduct disorders includes juvenile sexual offenders; when they remain in the community interventions such as multisystemic family has been found to be helpful in a randomized effectiveness trial.
[18]

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Mortality, Morbidity, and Comorbidity

The developmental courses of the 2 types of conduct disorder (CD) are somewhat predictable. Without appropriate intervention, children with childhood-onset CD develop high rates of substance abuse, risky sexual behavior, and nonintentional injuries as they move toward adulthood.
[19] They also frequently progress to the development of antisocial personality disorder. This disorder is an adult pattern of the same behaviors marked by a callous disregard of other persons and societal rules. The course for individuals with adolescent-onset CD is somewhat better. If appropriate social skills with peers are developed and essential academic skills are acquired, usually after intervention, most of these adolescents dramatically reduce their rate of conduct problem behaviors and move into a more productive pattern in their early adult years. This improved prognosis is particularly true of individuals who do not have a history of aggression and whose conduct problems are primarily property crimes (eg, stealing).

For all persons diagnosed with CD, co-occurrence with ADHD is at least 50%. While discriminating between conduct and attentional disorders may be possible, the practical use of this discrimination may be limited, given the high correlation of these disorders, particularly in younger children.

High comorbidity exists between the externalizing disorders and a number of internalizing disorders, such as anxiety and affective disorders (eg, depression). Cross-sectional studies of individuals with CD and these disorders indicate comorbidity of 32–37%. Again, the negative, inconsistent, impatient, or unresponsive parenting style of a depressed or anxious parent can contribute to the picture of CD in a child who does not develop antisocial personality disorder later in life.

Finally, a high comorbidity with academic failure and possible learning disabilities exists. Thus, complexity of this disorder appears to be the norm, rather than the exception. Estimates state that at least 60% of children with CD are likely to display one or more additional mental health or learning disorders. Because of this, successful assessment and intervention is multidisciplinary, usually requiring several components of medical, mental health, case management, and educational intervention.

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Academic Problems

Cognitive or academic deficits are the most widely reported educational correlates of conduct disorder (CD). An association between achievement deficits and disruptive behavior has been found as early as first grade and is an important predictor of outcome during elementary and middle school. These findings extend to early adult life in longitudinal studies. In a large epidemiologic study, children aged 11 years with reading disorders were 3 times as likely to exhibit some acting-out behavior problems.

The relationship between academic problems and conduct problems is not clear. Research performed in the late 1960s indicated that delinquency progressed from academic failure to antisocial behavior. The assumption was that academic failure led to loss of self-esteem, helplessness, decreased teacher and parent attention, and, ultimately, acting out to escape academic demands or dropping out of school to escape. Thus these individuals were not educated or trained to function successfully in the open unstructured society of the adult world as conduct problems, when present at the start of the school experience, interfere with learning.

In a second hypothesis, CD and poor achievement are functions of dysfunctional outside variables (eg, low socioeconomic status, an attention deficit disorder, nonsupportive family environment). These variables inadvertently support the conduct difficulties and do not support school achievement.

In a third hypothesis, some individuals with CD and poor achievement especially those with reading disorder (dyslexia) have an underlying disorder of cognitive processing called the Hebb repetition effect, which includes selective impairment in cognitive tasks that involve processing of serial order, even for nonverbal modalities.
[20]

Despite a lack of clear causal links, academic problems are linked with conduct problems; a comprehensive treatment program is required to assess and address the academic difficulties in conjunction with the behavior problems. Thus, in developing a plan for children with conduct problems, the primary health care provider should request that the school (1) evaluate the child for academic difficulties and (2) provide appropriate educational services to address those needs and other behavioral needs. If the school is unable or unwilling to carry out needed educational assessments, the primary health care provider needs to assist the family to obtain those educational assessments through other venues, such as university settings or private offices.

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Medical Treatment

Because of the multifaceted nature of conduct problems, particularly related comorbidities, treatment usually includes medication, teaching parenting skills, family therapy, and consultation with the school.
[21] Studies have shown that youth with severe aggression are not likely to respond without medication and they have a better response to a multimodal approach that should include attention to the development of social skills.
[22]

Alternatives to medication treatment or restraint for aggressive behavior may be helpful and some inpatient and residential programs for aggressive acting out youth are beginning to develop effective protocols.
[23] One promising, peer-led intervention for conduct disorder reported significant reduction of child behavior problems and improvement in parenting competencies. A large majority of parents (92%) completed the manualized program and reported improvements in all outcome measures, including child problems (number and severity), parental stress, and parenting competencies. Although a well-done study, it did not report data on long-term outcome as the children and parents were only studied before the start of the 8-week program and at completion.
[24]

Because of the high degree of overlap between CD and ADHD, the clinician should perform an evaluation for ADHD symptoms. Pharmacologic treatment for ADHD is indicated if the child has the symptoms of that disorder (see Attention-Deficit/Hyperactivity Disorder). To make that diagnosis, a thorough history, the presence of 6 of the 9 inattention or hyperactivity symptoms as specified in the DSM5, and clear impairment of functioning in at least 2 settings (usually home and school) are necessary.
[25]

In the short term, stimulant medicine has proven effective in controlling the specific symptoms of inattention, impulsivity, and hyperactivity. However, by itself, stimulant medication usually does not always result in improved parent-child, teacher-child, or peer relationships.
[25]

A study by Gadow et al. looked at the 52-week clinical outcomes of children whom parents rated as impaired due to their co-occurring attention-deficit/hyperactivity disorder (ADHD), disruptive behavior disorder, and serious physical aggression. The study compared the relative efficacy of basic treatment (parent training + stimulant medication + placebo) and augmented treatment (parent training + stimulant + risperidonerisperidone). Side effects from augmented treatment included elevated prolactin levels. However, the group that received stimulant medication only also reported side effects (eg, decreased weight over time). Both stimulant-only and risperidone treatment were associated with clinical improvement. However, if there is bipolar disorder, risperidone may be a more appropriate choice.
[26, 22]

Lithium and methylphenidate reduced aggressiveness in one set of studies; however, in subsequent follow-up research, the effectiveness of lithium could not be replicated. Studies have shown an association with marijuana use and increased rates of sexual aggression thus medications such as lithium may be helpful as they have been shown to decrease drug-related craving and thus decrease abuse of alcohol and illicit drugs.
[27]

Carbamazepine also has been demonstrated to be effective in treating aggressive behavior. Carbamazepine was effective in a pilot study; however, multiple significant adverse effects occurred. Note that substance abuse occurs in a high number of children with CD independent of whether they are treated with psychoactive medication. Physicians should use caution when prescribing stimulants and certain antipsychotic medications such as seroquel (quetiapine) because they can be sold illegally.

Thus, the first choice for treatment is stimulants due to their relatively safe side effect profile however when misuse/diversion is a risk the choice of medications that are less abusable such as Daytrana (methylphenidate in patch form) or Vyvanse (lis-dexamfetamine -medication is oral however bound to lysine requiring stomach acid digestion in order to be activated). Anticonvulsants are considered to be the second group of medications to be used in nonspecific aggression, and lithium is the third choice.

A fourth drug, guanfacine, which recently was approved by the FDA in a 24 hours form (Intuniv) for ADHD has been explored in an open trial with 15 of 17 patients exhibiting significantly decreased aggressive behavior; however, this medication requires monitoring of blood pressure and cardiovascular parameters-electrocardiogram is required before starting due to potential risk of heart block.

A fifth drug, divalproex has a less favorable safety profile than stimulants; however, it does not have the associated metabolic abnormality and risk of tardive dyskinesia that atypical antipsychotics and typical antipsychotic medications have. Thus, this is another possible choice for refractory aggression especially as it has been used safely with pediatric populations with epilepsy.
[28, 29]

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Psychological Treatment

Of the psychological therapies, parent management training (PMT) is the method demonstrated to have the most impact on the child's coercive pattern of behavior. PMT refers to procedures in which parents have been trained to alter their child's behavior in the home. PMT is based on research demonstrating that conduct problems inadvertently are developed and sustained by maladaptive parent-child interactions. While this conflictual interaction often is triggered by the irritable temperament in the child, a major component of this pattern is ineffective parenting. This includes the parent directly paying attention to disruptive and deviant behaviors but using unclear vague commands and directions and inconsistently applied harsh punishment. A pattern of failing to pay attention to appropriate behaviors, when they occur, is also present.

PMT alters the pattern of ineffective parenting by encouraging the parent to practice prosocial behavior (positive, specific feedback for desirable behavior), employ the use of natural and logical consequences, and use effective, brief, nonaversive punishments on a limited basis when specific encouragement and consequences are not applicable.

PMT educators and therapists teach the child's parents to use specific procedures at home to alter interactions with their child. Parents are trained to carefully identify and observe behaviors and to reinforce desired behaviors. Training sessions provide opportunities to see how procedures work and to practice and refine their use of techniques.

In treating groups of preschool children who had severe oppositional and aggressive behavior, some evidence-based parenting therapies exist. In these clinical random assignment studies, when therapists adhered to a manual of techniques and parents made changes in parenting skills (which were documented), the outcome included immediate posttreatment improvement and evidence of improvement 1–3 years after treatment. One study reflected gains 10 years later. Treatment effects have been stronger with younger children but have also co-varied with the severity of the problems. Children with the most severe problems are more resistant to improvement.
[30, 31] A parental training program for early intervention with preschoolers at risk for conduct problems was shown in one study to improve dispositional variables post-intervention and at one-year follow-up.
[32]

More recent research suggests that the severity of the problem, rather than the age of the child, is predictive of treatment failure. Severe conduct problems in adolescents are the most resistant to this type of treatment, when compared with younger children. However, with appropriate treatment programs, some improvement has been documented in all age ranges and all levels of severity. Treatment needs to be highly structured with specific goals and the use of established behavioral techniques to improve communication and problem solving skills, as well as the reinforcement of prosocial behaviors and the implementation of clear discipline for inappropriate behaviors.
[33]

Group treatment has had both benefits and drawbacks for children with conduct disorder (CD). While some evidence exists that group social skills or problem-solving treatment has some benefit in children aged 12 years and younger, concerns exist about group treatment of adolescents diagnosed with CD. With younger children, combined treatment in which parents attend a PMT group while the children attend a social skills group consistently has exhibited good effect. However, research demonstrates that treatment of adolescents with CD conducted in groups of individuals with CD tends to worsen the behavior, particularly if the group participants engage in discussions of oppositional and illegal behaviors.

Thus, group treatment should be enacted with great care and consideration of group goals and possible negative adverse effects. More drastic solutions (eg, boot camps) consistently have demonstrated initial good outcome but worsening outcome in the long term, with higher rates of arrests and serious crimes found in boot camp graduates. Poor long-term outcome following this treatment is believed to be due, in part, to group mutual reinforcement and discussion of criminal activity and to the lack of family or community change in many of these programs. Thus, the adolescents are released back into the same environment, in which little support for the newly acquired skills and behavior is present.

In general, individual psychotherapy as a single treatment has not proven effective for conduct problems. However, individual therapy sessions certainly can facilitate compliance with an overall program that emphasizes changes in the family, the school, and in social settings. Thus, individual counseling may help a child who is trying to adhere to a more comprehensive intervention program.

The multisystemic treatment package is a comprehensive model of treatment of CD that includes behavioral PMT, social skills training, academic support, pharmacologic treatment of ADHD or depression symptoms, and individual counseling as needed. Initial outcome data for this type of comprehensive approach have been encouraging.

Multisystemic therapy has been proven to be helpful for children and adolescents with CD, especially when parent management has been attempted unsuccessfully.
[34, 35, 36]

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Early Identification

A study by Wong, Raine, and Venables found that being left home alone at age 3 years may increase the risk of conduct disorder at age 17 years and schizotypy and antisocial behavior at age 23 years; this effect was not accounted for by social or ethnic factors and appeared to be a sleeper effect as conduct disorder symptoms did not seem to emerge at earlier age.
[37]